The “monster” was snapped off Seacombe Ferry at 9am yesterday by photographer Mark Harrison.

Paul Renolds, from the Blue Planet Aquarium, who studied the photos, said: “It is virtually impossible to actually identify, but this is the time of year when large numbers of basking sharks, the second largest shark species in the world after whale sharks, head towards waters off the Isle of Man.”

He added: “If it is not a basking shark, it could be a smaller species of whale or a dolphin because there are around 23 different species in UK waters.”